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Describe the relationship among the various hemoglobin's in first year of life and their implication in diagnosing hereditary hemoglobinopathies.

Hemoglobin is tetramer of 4 globin chain + heme( Fe containing porphyrin ring).

Hb F has 2 alpha chains and 2 beta chains which is replaced by Hb A which has 2 aplha chains and 2 beta chains.

Hemoglobin F   -   α2 γ2

Hemoglobin A   -  α2 β2

Normal replacement goes as below

  • By 6-8wk HbF is predominate hb
  • By 24wk 
    • HbF constitute 90% of Hb
    • HbA constitute 5-10% of Hb
  • By 6-12mo postnatal age
    • HbF is <2% of total Hb
    • HbA reaches adult level
There could be deviations in this replacement due to mutations in gene which cause replacement of amino acids and forms defective hemoglobins.
Diagnosis is done by HPLC (High Performance Liquid Chromatography) or IEF (Thin layer/Isoelectric Focusing). 

F - fetal Hb
S - sickle Hb
SS - Homozygous SCD
AS - Sickle cell trait
Sβ - Sickle thalassemia
C -  Hb C
SC - sickle-hemoglobin C
A stands for adult Hb
HPFH - Hereditary Presence of Fetal Hemoglobin

Hb are written from greater to lower quantity.

Report

Possibilities

FS

  • SCD SS

  • SCD Sβ thal

  • S HPFH

FSC

  • SCD SC

FSA

  • SCD Sβ thal (Hb S>50%, HbA2>3.5%)

FAS

  • SCD AS (rule out blood transfusion)

AFS

Transfusion is received so can be

  • SCD SS

  • SCD Sβ thal

FS Other

  • SCD Sβ thal

  • SCD SD, SO, SC, S


F98%A22%

β thalassemia major

A65-88%F10-30%,A22-5%

β thalassemia intermediate

↑ A2, variable F

β thalassemia trait

A2 absent

𝛿 thalassemia

Bart: 1-2%

α thalassemia 1 gene deletion

Bart: 5-10%

α thalassemia 2 genes deletion

Bart: 20-30%

α thalassemia 3 genes deletion

Bart: 90% c Grower 1,2 & Portland

α thalassemia 4 genes deletion

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